Trump keeps talking about how most NATO members are not meeting the target goal of 2% of GDP on military spending. While it is clear that the US spends well above this figure (~ 4.7% of GDP for FY 2010), how much of that can be considered NATO-related spending?
Pretty much 100% of most European NATO members military spending should be considered as dedicated to NATO, with some part of the UK and possibly French spending related to overseas defence other than NATO. The US, on the other hand, has a large amount of its military spending for the Pacific, including Korea and Japan, for Western hemisphere defence, including drug enforcement, and other non-NATO areas. It has also had major reductions in forces assigned to Europe. So how much of the 4.7% actually counts as “NATO” spending? Does the US actually meet the 2% target itself?
I can’t provide a full answer at the moment, but any answer beyond how much it costs the US to maintain bases in Europe - a few billion a year - is going to be an arbitrary answer. (There are of course more costs than this to our presence, but that’s mainly just supporting the bases.)
The Air Force has something like fifty-odd fighter squadrons. If we go to war with Russia because of NATO commitments, a lot of them will be in the fight. But if we go to war with Iran, an awful lot of them are going to be in that fight. There isn’t any realistic way to say that some percentage of those squadrons are “for” NATO as opposed to “for” Syria, North Korea, China, or anywhere else.
The 2% target doesn’t mean member states have to spend 2% of GDP on NATO-related stuff. It’s just a minimum spend for defense generally. The idea is that if members spend X amount on their defense capabilities, Y amount of that capability will be available for NATO missions.